Technical Field
The invention relates to the field of characteristics of mechanical stress testing of solid materials, in particular to a handheld constant-stiffness ring shear apparatus and a using method thereof.
Description of Related Art
The ring shear apparatus was developed in the 1920s, however development of the ring shear apparatus almost stopped in the several decades following. Study on the ring shear apparatus began again in the 1960s along with the rise of studies on residual strength, and afterwards, various ring shear apparatuses used in indoor laboratories have been researched and developed.
Existing indoor ring shear apparatuses can be of two types, namely single-ring shear apparatuses and double-ring shear apparatuses, according to the structural characteristics. Compared with other soil test methods, the ring shear apparatuses have the two common advantages that during the test process, the area of the shear plane can be kept unchanged and shearing can be conducted under a continuous displacement condition. According to single-ring shear apparatuses, during the test process, a soil sample is placed into a cylindrical sample box, and vertical pressure and torsional shear force are applied to the sample through a pressurization plate on the upper portion. The single-ring shear apparatuses mainly have the advantage that leakage of the soil sample can be avoided during the shear test process. According to the double-ring shear apparatuses, a soil sample is sheared along a preset plane in the middle of the annular shear boxes which are mutually independent in the vertical direction, so that the purposes of lowering distribution non-uniformity of stress and strain along the shearing plane, reducing resistance between the soil sample and shear rings, and eliminating stress concentration of the edges of the shear rings are hopefully realized.
With the improvement of the technical means, the non-drainage state can be achieved in the shear process under various test conditions by a modern indoor ring shear apparatus through a servo control system and a shear ring seam sensor, and implementation and switching of a drainage test condition and a non-drainage test condition can be guaranteed, and meanwhile, test data can be analyzed and processed more conveniently and faster by the application of computer-controlled and high-sensitivity recording equipment. However, since a modern ring shear test system is increasingly complex and precise, the manufacturing cost and using cost of the modern ring shear apparatuses are increasing gradually, and the daily maintenance fee of the apparatuses is becoming increasingly high. In addition, the existing ring shear apparatuses are complex and large in size, can only be used in an indoor laboratory, cannot be used at a field location, and can only output constant pressure.